Storage systems configured from RAID (Redundant Array of Independent (or Inexpensive) Disks) are being used widely today to safely store corporate data. In addition, thin provisioning is being introduced to enhance the utilization efficiency of storage system capacity.
In a RAID system, a RAID group is configured from a plurality of storage devices, and a logical volume is configured on the RAID group. In a storage system that does not use thin provisioning, the logical volume is provided to a host, and a storage area of a storage device having a capacity that is equivalent to the entire storage capacity of the logical volume is allocated to this logical volume from the time the logical volume is created. By contrast, in thin provisioning, in which a virtual volume is provided to the host, a storage area of the storage device corresponding to the initial virtual storage area is not allocated to the virtual storage area inside this virtual volume, but rather, the storage area of the storage device that is allocated to the logical volume is allocated only to the virtual storage area when there has been a write request with respect to the virtual storage area. For this reason, only a storage device of the capacity required for the time being is provided when the storage system is introduced, and a storage device can easily be added as the need arises.
As a thin provisioning technique, Patent Literature 1 proposes a method for rearranging data on a plurality of storage devices in logical volume units in a storage system that uses thin provisioning.
Further, Patent Literature 2 proposes a method for adding storage devices in storage device units by changing the data redundancy configuration after adding a storage device.